1. Field of the Invention
This invention relates to an information recording method for recording data and directories for controlling the data on a recording medium.
2. Related Background Art
A floppy disc using magnetism to effect recording and reproduction and a card-like optical information recording medium (hereinafter referred to as the optical card) using light to effect recording and reproduction are known as information recording mediums. In these information recording mediums, auxiliary data for controlling data for each type, i.e., so-called directories, are used to store a large capacity of data therein. A directory usually has written therein file information such as the name of the file, the length of the file and the head data track number, whereby file control of the data track portion is effected.
The optical card, particularly, the nonerasable postscript type optical card, has a large capacity of recording even if the dimensions thereof are the same as the size of a credit card. The dimensions of the credit card are about 85 mm .times. 55 mm, and when the information track pitch is 20 .mu.m and the record length of 1 bit is 5 .mu.m,
the number of tracks is 55.div.(20.times.10-3)=2750, PA1 the bit capacity/track is 85.div.(5.times.10-3)= 17000 (bits), PA1 the byte capacity/track is 17000.div.8=2000 (bytes). PA1 2750.times.2000=5500000=5.5 (M bytes).
Accordingly, the total data capacity is
To control such a large capacity of information, the information control technique using directories is indispensable.
FIG. 1 of the accompanying drawings a schematic plan view showing an example of such an optical card. In FIG. 1, data tracks 10.sub.1, 10.sub.2, . . . , 10.sub.n are recorded in the recording area of the optical card 1 in succession from one end thereof in the direction of arrow E. Each data track comprises a data portion 12 and an address portion 11 indicative of the track number. Also, directories 20.sub.1, 20.sub.2, 20.sub.3, 20.sub.4, . . . for controlling said data are written in the fashion of postscript in the direction of arrow D from the other end of the recording area. Such a recording method is described in detail in Japanese Laid-Open Patent Application No. 279957/1986.
However, in the above-described recording method, the data are arranged in order of time of recording. Therefore, when reproducing these data, the necessary files (the data groups associated with one another) are not always arranged in a grouping.
Assuming, for example, that there is an information recording medium on which a certain doctor has recorded data such as electrocardiograph information and brain-wave information of a certain patient from one year of age until fifteen years of age, the electrocardiograph information and the brain-wave information at one year of age, the electrocardiograph information and the brain-wave information at two years of age, and so on are recorded on that information recording medium in the fashion of postscript. Accordingly, when the need to reproduce only the electrocardiograph information from that information recording medium occurs, access to the data file will be desultory and the access time will be long.
Also, when there is a large defect in the information recording medium and there is an area in which recording and reproduction is impossible, it is desirable to use the recording medium while avoiding that area in order to improve the recording-reproducing speed. However, in the recording method according to the prior art, there has been the problem that directories become complex to evade the defective area and the control of data becomes cumbersome.